I played UO 98-99 on Europa. Back then I enjoyed being able to play a game where I could do smithing almost exclusively. Just hanging out with other people who enjoyed a very small aspect of the game, and being able to service others. There was a nice feeling of earning the trust of a community (people had to give you their things for you to fix, and you could theoretically just keep them, but play enough and your character built a reputation as a reliable person in the community, rather than having it rules based or anything) that hasnt been in place in other MMOs that I've played.

I went back to play it last year I think, and it was still an enjoyable, but thoroughly broken game world. For me it was mostly nostalgia, and after a few months of playing it vaned, but the content still held up surprisingly well, especially as it was never really meant to be balanced.